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Raised voices and deep discussions will fill the 49ers‘ upper offices Friday, when coaches and executives determine the shape of their final 53-man roster.

Certain players could sway opinions with their performances Thursday in the team’s final preseason tune-up against the Chargers, a fact quarterback Scott Tolzien made clear this week to several fringe players.

“The bottom line is, it doesn’t matter who you’re playing against or what’s at stake – you want to play your best all the time,” Tolzien said “You’re a competitor and you want to put out good film for all the teams to see. That’s the bottom line.”

Tolzien lived those words last year, when he completed 16 of 23 passes for 226 yards with one touchdown and one interception against the 49ers in the preseason. When San Diego released Tolzien, the 49ers quickly claimed him.

After another impressive training camp this season, Tolzien is nearly a lock to stay with San Francisco.

But other decisions will be harder to make, particularly with talent bulging at quarterback, running back and wide receiver. It could lead to an oddly shaped roster such as last season’s, which included six safeties.

This year, it’s conceivable the 49ers could keep seven running backs, with bubble players Anthony Dixon and Rock Cartwright making the team along with Frank Gore, Bruce Miller, Kendall Hunter, Brandon Jacobs and rookie LaMichael James.

Dixon and Cartwright provide a special teams element, and if Jacobs’ knee is not recovered by the 49ers Sept. 9 opener in Green Bay, Dixon would be the only big back in the fold.

But carrying so many running backs means going short somewhere else, like at tight end or outside linebacker. Last year, the team retained two tight ends to start the season and then signed veteran Justin Peelle.

The 49ers could do the same thing again and wait for defensive end/tight end Demarcus Dobbs to heal from his left leg injury.

Dixon and Cartwright still need to show well, as does former Stanford tight end Konrad Reuland and safeties Michael Thomas, Colin Jones, and Trenton Robinson. Let’s hope all of them listened well to Scott Tolzien.

Thursday’s game

Who: Chargers vs. 49ers

Where: Candlestick Park

When: 7 p.m.

TV/Radio: Channel: 44 /810, 107.7

Kevin Lynch is SFGate.com’s Niner Insider. For more, see blog.sfgate.com/49ers.